Abstract: A novel class of solvents is described that have improved selectivity for H.sub.2 S as compared to CO.sub.2. The solvents are based on adding suitable second partially miscible solvent to known solvents. In specific, it is shown that adding 20% of dodecane to NMP (normal methyl pyrolidinone) increases the selectivity of the solvent for H.sub.2 S as compared to CO.sub.2 by 50%. This leads to important process improvements and reduction in the cost of the removal process.

Abstract: A multistage countercurrent separation apparatus and method is described. Each stage includes a mixer zone and a settler zone, both of which have temperature control means to achieve a first temperature and a second temperature, respectively, in the mixer and settler zones. Solvents used in the process are selected so that they have at least one immiscibility transition temperature such that they form a single homogeneous phase at said first temperature and two heterogeneous phases at said second temperature. By carrying out the process, a solute or solutes introduced into the system may appropriately be efficiently concentrated or separated with minimal agitation. Furthermore, because emulsification by rapid agitation is avoided, the homogeneous phase quickly coalesces upon passing into the heterogeneous phase, thereby increasing the throughput which may be achieved by the extraction process.